The present invention relates to optical examination apparatus, and particularly to a novel method and apparatus for optically examining an object. The invention is particularly useful in moire ray deflection mapping for determining properties of an object, and is therefore described below with respect to this application.
U.S. Pat. No. 4,459,027 by Oded Kafri, one of the inventors of the present application, and Aminadav Livnat, describes a method and apparatus for mapping an object using moire deflectrometry, wherein a collimated beam deflected from the object is used to generate a moire pattern by directing the collimated beam to first and second gratings at a preselected angular orientation and separation with respect to one another, the moire pattern so produced providing an indication of the properties of the examined object.
This technique has proved itself as an efficient, straightforward, and relatively low-cost tool for optical testing. It enables comprehensive diagnostics of optical complements, and is fundamentally compatible with interferometry since the data, namely ray deflection angles, can be translated into phase retardation by integration. The technique applies equally well for phase objects and or specular surfaces, as described for example in O. Kafri and A. Livnat, "Reflective Surface Analysis Using moire Deflectometry", Appl. Optics 20, 3098-3100 (1981). The sensitivity of the method, or alternatively, the spatial resolution, can be enhanced by applying telescopic or microscopic modes of operation, as described in the publications O. Kafri and I. Glatt, "moire Deflectometry--A Ray deflection Approach to Optical Testing", Optical Eng. 24, 944-60 (1985); and J. Krasinski, D. F. Heller, and 0. Kafri, "Phase Object Microscopy Using moire Deflectometry", Appl. Optics 24, 3032-36 (1985), respectively. In the microscopic mode, the beam is expanded after passing through the test object, thus reducing the angular sensitivity and increasing the spatial resolution of the instrument. In the telescopic configuration, on the other hand, a reverse process is carried out, in which the angular resolution is increased at the expense of the spatial resolution.